Objective:

The objective of this project is to utilize wholly aqueous systems, such as polymer-based aqueous biphasic systems, as an environmentally benign extraction media for the separation of reaction products during the pulping process, and thus reducing chemical and energy consumption, eliminating emissions, and increasing the efficiency of the pulping process.

Progress Summary:

We investigated the effect of the addition of polymers to a standard pulping
solution on Kappa number, pulp yield, and residual alkali of softwood and mixed
hardwoods under temperatures and pressures equivalent to current alkaline
paper-pulping practices. As the result of the addition of polymer to the
process, less energy was needed to produce similar Kappa numbers and achieve
pulp yields that far exceed those measured for bleachable pulps in a Kraft
process. The addition of polymer to the process also yielded an increase in
residual alkali found in the cook. The more residual alkali left in the cook
indicates fewer chemicals were consumed in the process, and as a result, more
chemicals are available for recycling.

We have begun to develop a kinetic model to describe delignification in
polymer-base aqueous biphasic systems. These models enable us to compare each of
the pulping processes we have studied based on activation energy. From the
activation energy, we can determine the most energy efficient process. We have
found that the addition of polymer to the process results in lowering the
activation energy. Lower activation energy results in less energy and lower
temperatures needed to run the process.

Effective design and use of aqueous biphasic separation strategies involving
polyethylene glycol require an understanding of why these systems form two
distinct phases and how solutes partition themselves between the phases. From a
molecular thermodynamics point-of-view, this means developing an understanding
of how the molecular architecture and inter- and intra-molecular interactions
govern the Gibbs free energy of the solution. We have been simulating ethylene
glycol oligomers. In particular, we have been conducting Monte Carlo simulations
of a particular model for the system. This model uses a united atom
representation for the polymer chains with potential parameters obtained from
the literature. The results indicate that the conformational populations change
around the C-C bonds in intriguing ways with both polymer concentration and temperature.

Future Activities:

Semi-batch extraction/reaction systems will be used to simulate separations
of lignin from the cellulose fraction of wood under realistic conditions. These
results will be compared to those obtained from the batch experiments and to
those obtained from the traditional Kraft pulping process to determine the
benefits of adding polymer to the chemical pulping process.

We are developing analytical techniques to identify and study the raw
materials that are left behind in each of the two phases of the cook after
pulping. We also are investigating new materials that could be obtained from
lignin using an enzyme to depolymerize lignin into smaller aromatic constituents.

Relevant Websites:

Progress and Final Reports:

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.